The present invention relates color negative films and their chemical processing. The films are especially suitable for loading into one-time-use cameras and are intended to create images for scanning, electronic manipulations, and reconversion to a viewable form.
The term xe2x80x9cone-time-use cameraxe2x80x9d or xe2x80x9cOTUCxe2x80x9d is used to indicate a camera supplied to the user preloaded with a light sensitive silver halide photographic element and having a lens and shutter. The terms xe2x80x9csingle-use camera,xe2x80x9d xe2x80x9cfilm-with-lens unit,xe2x80x9d xe2x80x9cdisposable cameraxe2x80x9d and the like are also employed in the art for cameras that are intended for one use, after which they are recycled, subsequent to removal of the film for development.
The term xe2x80x9cExe2x80x9d is used to indicate exposure in lux-seconds.
The term xe2x80x9cgammaxe2x80x9d is employed to indicate the incremental increase in image density (AD) produced by a corresponding incremental increase in log exposure (xcex94log E) and indicates the maximum gamma measured over an exposure range extending between a first characteristic curve reference point lying at a density of 0.15 above minimum density and a second characteristic curve reference point separated from the first reference point by 0.9 log E.
The term xe2x80x9ccouplerxe2x80x9d indicates a compound that reacts with oxidized color developing agent to create or modify the hue of a dye chromophore.
In referring to blue, green and red recording dye image-forming layer units, the term xe2x80x9clayer unitxe2x80x9d indicates the hydrophilic colloid layer or layers that contain radiation-sensitive silver halide grains to capture exposing radiation and couplers that react upon development of the grains. The grains and couplers are usually in the same layer, but can be in adjacent layers.
The term xe2x80x9cexposure latitudexe2x80x9d indicates the exposure range of a characteristic curve segment over which instantaneous gamma (xcex94D/xcex94log E) is at least 25 percent of gamma, as defined above. The exposure latitude of a color element having multiple color recording units is the exposure range over which the characteristic curves of the red, green, and blue color recording units simultaneously fulfill the aforesaid definition.
The term xe2x80x9cgamma ratioxe2x80x9d when applied to a color recording layer unit refers to the ratio determined by dividing the color gamma of a cited layer unit after an imagewise color separation exposure and process that enables development of primarily that layer unit by the color gamma of the same layer unit after an imagewise white light exposure and process that enables development of all layer units. This term relates to the degree of color saturation available from that layer unit after conventional optical printing. Larger values of the gamma ratio indicate enhanced degrees of color saturation under optical printing conditions.
The term xe2x80x9ccolored masking couplerxe2x80x9d indicates a coupler that is initially colored and that loses its initial color during development upon reaction with oxidized color developing agent.
The term xe2x80x9csubstantially free of colored masking couplerxe2x80x9d indicates a total coating coverage of less than 0.09 millimole/m2 of colored masking coupler.
The term xe2x80x9cdye image-forming couplerxe2x80x9d indicates a coupler that reacts with oxidized color developing agent to produce a dye image.
The term xe2x80x9cabsorption half-peak bandwidthxe2x80x9d indicates the spectral range over which a dye exhibits an absorption equal to at least half of its peak absorption.
The term xe2x80x9cdevelopment inhibitor releasing compoundxe2x80x9d or xe2x80x9cDIRxe2x80x9d indicates a compound that cleaves to release a development inhibitor during color development. As defined DIR""s include couplers and other compounds that utilize anchimeric and timed releasing mechanisms.
In referring to grains and emulsions containing two or more halides, the halides are named in order of ascending concentrations.
In referring to grains, xe2x80x9cECDxe2x80x9d indicates mean equivalent circular diameter and, in describing tabular grains, xe2x80x9ctxe2x80x9d indicates mean tabular grain thickness.
The term xe2x80x9caverage aspect ratioxe2x80x9d when used in reference to tabular emulsion grains, refers to the ratio of mean tabular grain equivalent circular diameter to mean tabular grain thickness.
The term xe2x80x9caspect ratioxe2x80x9d when used in reference to an image refers to the ratio of image length to height as recorded on an element or as provided in viewable form.
References to blue, green, and/or red spectral sensitizing dyes indicate dyes that absorb blue, green, or red light and transfer the absorbed photon energy to silver halide grains when adsorbed to their surfaces.
Research Disclosure is published by Kenneth Mason Publications, Ltd., Dudley House, 12 North St., Emsworth, Hampshire PO10 7DQ, England.
There are a variety of one-time-use cameras that have provided amateur photographers with a low cost means of taking satisfactory pictures. Such cameras have been provided with lenses, shutters and film advance mechanisms. They are intended for one use, after which they are recycled, subsequent to removal of the film for development. While prior one-time-use cameras were satisfactory for many purposes, there remain problems with their performance. Such one-time-use cameras require a sensitive film and a short shutter time to reduce sharpness losses caused by motion of the camera during picture taking. However, high speed, high sensitivity films tend to be lower in sharpness and higher in grain than lower sensitivity films with the result that their use in such cameras leads to pictures that are inadequate for many purposes. The sharpness problem can be exacerbated by the poor quality of the lenses often employed in these one-time-use cameras. This problem is even more severe when one attempts to provide one-time use cameras that will provide negatives that are suitable for production of large prints by high magnification enlargement. Further, there is a desire in one-time-use cameras to provide more pictures from each camera. One way to do this would be to provide a smaller negative, thereby allowing the same amount of film to record more images. However, since the negatives were not satisfactory for high magnification enlargements, it was not possible to minimize the size of the negatives exposed without having a deterioration in the sharpness and graininess of the prints formed from the negative. Additionally, there would be fewer ecological concerns if more negatives could be taken on the same amount of film as there would be less generation of chemicals during development per print as well as more negatives taken per single-use camera. Further, these one-time-use cameras require a long latitude film since exposure control on the cameras is limited to non-existent and the only way of ensuring adequate picture taking ability in a variety of picture-taking situations is by designing the film to be adequately responsive to a wide variety of lighting conditions.
Color negative photographic elements are conventionally formed with superimposed blue, green and red recording layer units coated on a support. The blue, green, and red recording layer units contain radiation-sensitive silver halide emulsions that form a latent image in response to blue, green, and red light, respectively. Additionally, the blue recording layer unit contains a yellow dye image-forming coupler, the green recording layer unit contains a magenta dye image-forming coupler, and the red recording layer unit contains a cyan dye image-forming coupler. Following imagewise exposure, the photographic elements are processed in a color developer, which contains a color developing agent that is oxidized while selectively reducing latent image-bearing silver halide grains to silver. The oxidized color developing agent then reacts with the dye image-forming coupler in the vicinity of the developed grains to produce an image dye. Yellow (blue-absorbing), magenta (green-absorbing), and cyan (red-absorbing) image dyes are formed in the blue, green, and red recording layer units respectively. Subsequently the element is bleached (i.e., developed silver is converted back to silver halide) to eliminate neutral density attributable to developed silver and then fixed (i.e., silver halide is removed) to provide stability during subsequent room light handling.
When processing is conducted as noted above, negative dye images are produced. To produce a viewable positive dye image and, hence, to produce a visual approximation of the hues of the subject photographed, white light is typically passed through the color negative image to expose a second color photographic element having blue, green, and red recording layer units as described above, usually coated on a white reflective support. The second element is commonly referred to as a color print element, and the process of exposing the color print element through the image bearing color negative element is commonly referred to as optical printing. Processing of the color print element as described above produces a viewable positive image that approximates that of the subject originally photographed.
A problem with the accuracy of color reproduction delayed the commercial introduction of color negative elements. In color negative imaging two dye image-forming coupler containing elements, a camera speed image capture and storage element and an image display, i.e. print element, are sequentially exposed and processed to arrive at a viewable positive image. The dye image-forming couplers each produce dyes that only approximate an absorption profile corresponding to that recorded by the silver halide grains. Since the color negative element cascades its color errors forward to the color print element, the cumulative error in the final print is unacceptably large, absent some form of color correction.
A commercially acceptable solution that remains in use today in the form of color slides is to subject a color photographic element having blue, green and red recording layer units to reversal processing. In reversal processing the film is first black-and-white processed to develop exposed silver halide grains imagewise without formation of a corresponding dye image. Thereafter, the remaining silver halide grains are rendered developable. Color development followed by bleaching and fixing produces a viewable color image corresponding to the subject photographed. The primary objections to this approach are (a) the more complicated processing required and (b) the absence of an opportunity to correct underexposures and overexposures, as is provided during exposure of a print element.
Commercial acceptance of color negative elements occurred after commercial introduction of the first color reversal films. The commercial solution to the problem of cascaded color error has been to place colored masking couplers in the color negative element at concentrations of greater than 0.12 (and typically greater than 0.25) millimole/m2. Illustrations of colored masking couplers are provided by Research Disclosure, Vol. 389, September 1996, Item 38957, XII. Features applicable only to color negative, paragraphs (1) and (2). The colored masking couplers lose or change their color in areas in which grain development occurs producing a dye image that is a reversal of the unwanted absorption of the image dye. This has the effect of neutralizing unwanted spectral absorption by the image dyes and thereby providing more accurate color reproduction at a subsequent printing step. It also has the effect of raising the neutral density of the processed color negative element. However, this is not a practical difficulty, since this is easily offset by increasing exposure levels when exposing the print element through the color negative element. The color masking couplers increase the gamma ratios of the color recording layer units.
In this regard, it should be noted that colored masking couplers have no applicability to reversal color elements intended for direct viewing. They actually increase visually objectionable dye absorption in a color negative film, superimposing an overall salmon colored tone, which can be tolerated only because color negative images are not intended to be viewed. On the other hand, color reversal images are made to be viewed, but not printed. Thus colored masking couplers, if incorporated in reversal films, would be visually objectionable and serve no useful purpose. Additionally, since reversal color elements are intended for direct viewing, the dyes which form the image must be employed in a visually pleasing manner. This means providing a dye image having a dye gamma of two or greater in each color record, a requirement, which when combined with the density forming ability of couplers, effectively limits the exposure latitude of such elements to less than about 2.4 log E.
In addition to incorporating colored masking couplers in color negative photographic elements, it has been recognized that improved dye images can be realized by incorporating one or more developer inhibitor releasing compounds in the dye image-forming layer units. The development inhibitor, which is unblocked and increases in mobility by release during color development, improves the dye image by interacting with adjacent layer units to create favorable interimage effects and by sharpening dye image edge definition. These favorable interimage effects involve the imagewise retardation of development rates in several color records as a function of exposure and development in any one color record. The net effect is one of reducing dye density in one color record as a function of exposure and development in another color record, thus effectively neutralizing unwanted spectral absorption by the image dyes, and thereby providing more accurate color reproduction at a subsequent printing step. Illustrations of development inhibitor releasing compounds are provided by Research Disclosure, Item 38957, cited above, X. Dye image formers and modifiers, C. Image dye modifiers. These DIR compounds increase the gamma ratio of the color recording units.
Selection of suitable DIR compounds based on a measured diffusion factor is illustrated by Iwasa et al U.S. Pat. No. 4,524,130. Iwasa et al addresses the problem of providing color negative photographic elements that provide improved color print enlargements having increased sharpness and reduced graininess. The problem is addressed by employing in combination radiation-sensitive silver halide emulsion layers differing in iodide content and containing DIR""s having diffusion factors of 0.4 or higher. These choices in iodide content and DIR characteristics inherently provide high levels of color correction between the color records since the same diffusion mechanisms responsible for high intralayer sharpness induce high interlayer interimage effects and inherently produce color records having high gamma ratios. Iwasa et al makes no mention of adapting color negative photographic elements for producing images that are of improved quality when converted to digital form and then reconstructed for viewing.
It has thus become a near universal goal in modern silver halide color negative photography of seeking and employing high gamma ratio elements to achieve excellent color.
In color negative films in which silver coating coverages are significantly reduced, it is in some instances difficult to obtain a desired level of image discrimination (Dmax-Dmin) when masking couplers are present. The following patents include examples of color negative elements in which masking couplers have been omitted: Schmittou et al U.S. Pat. No. 5,183,727 (Element I), Sowinski et al U.S. Pat. Nos. 5,219,715 and 5,322,766 (Element III), English et al U.S. Pat. No. 5,318,880 (Sample 108), Szajewski et al U.S. Pat. No. 5,298,376 (Samples 301 to 312), and Lushington et al U.S. Pat. No. 5,300,417 (samples 300 to 310). In limiting silver coating coverages, these patents have not exhibited the degree of exposure latitude normally desired for color negative films. Further, the gamma ratios were still maintained at high levels so as to provide for the desired color properties after optical printing.
The operation of substantial levels of interlayer interimage in a typical color negative photographic element intended for optical printing is not without consequence, however. It is appreciated that chemical acutance enhancement that amplifies edge differences to increase print-through visual sharpness and interlayer interimage effects that build colorfulness in the silver halide color paper optical print also amplify the granular nature of the image areas rendered by the silver halide microcrystals as dye deposits. This image noise is termed graininess. The buildup of chemically derived image noise from chemical signal processing in color negative film presently limits the utility of high-speed photographic recording materials and lower speed materials intended for high magnification applications, such as 24 mm-frame size formats. Furthermore, high-speed films of the type desired for use in inexpensive cameras such as one-time-use cameras that lack exposure control because of its prohibitive cost generally suffer chemical performance limitations due to the properties of the very large silver halide emulsions that are required. It is not even possible to produce adequately high chemical interlayer interimage effects with them at any noise price and still retain high sensitivity. In addition, the high interlayer interimage requirements for more accurate emulsion spectral sensitivities are prohibitive in their cost to even low speed films intended for high magnification, because of image noise build-up without necessarily generating offsetting increases in film acutance performance that would counterbalance the noise increase.
It is coming to light that the digitization of processed color negative films by image scanning is an attractive process for creating electronic signals bearing trichromatic image information that are freed from many of the constraints of the optical printing system. For example, film contrast mismatches due to processing deviations that irreparably mar the resultant optical print can be adjusted and corrected to restore the image faithfulness to the original scene. But the process of scanning and adjusting image-bearing signals and writing them to an output medium, like the chemical signal processing due to interlayer interimage effects, also increases image noise. Ironically, it is required that the scanned image be blurred by a so-called low-pass filter to avoid the generation of color banding or aliasing artifacts, and then digitally resharpened to a pleasing level at the time of image printing. In the process, it is common to observe image noise well in excess of that produced by the counterpart optical print from the same color negative, albeit at higher print sharpness.
Upon further consideration, it will be appreciated that in the process of digitally preparing a viewable image from an optically printable color negative photographic recording material, the image-bearing signals recorded by the silver halide emulsions as latent image sites have, in fact, inadvertently been subjected to signal processing twice: the first chemical processing subjected the emulsion responsivities to chemical interlayer interimage effects to correct for imperfect image dye hues in the negative and silver halide color print material, and add edge sharpness, and the second electronic processing provided, following scanning and selective blurring, analogous spatially indiscriminate image amplification, color correction for imperfect image dyes, and edge sharpening. But it is uncertain that the second electronic signal processing derives any material benefit from the first chemical signal processing that preceded it. It is the object of one representative commercial electronic signal processing pathway, following scanning that produces image-bearing electronic signals from the color negative image dye deposits, to remove the chromatic interdependence of the signals by applying the precise inverse or reciprocal of the film chemical color correction matrix to them. While this procedure may adequately achieve the objective of removing the effects of chemical interlayer interimage effects on the image trichromatic densities derived from scanning, a question remains surrounding the treatment""s effect on image noise. In particular, at the usual tone scale and while maintaining color fidelity and image sharpness, would the noise of a digital image be reduced if the image bearing signals were subjected to significant signal processing just once? There remains a need for low graininess color photographic recording materials that have high sensitivity to capture images in inexpensive cameras lacking exposure control such as one-time-use cameras. A need is rapidly becoming evident for low-noise image-bearing signals following scanning that allow higher levels of electronic signal processing to further raise reconstructed viewable image colorfulness and sharpness to desired levels that are prohibitive or even wholly unattainable in systems that rely solely on chemical interlayer interimage effects to produce system color correction and edge enhancement.
In spite of this sustained effort, there remains a need for color films suitable for use in one-time-use cameras, which enable the production of viewable images having excellent color reproduction, low grain, and high sharpness following scanning and electronic conversion.
In one aspect this invention is directed to a one-time-use camera preloaded with a color negative photographic element for producing a color image suited for conversion to an electronic form and subsequent reconversion into a viewable form comprised of a support and, coated on the support, a plurality of hydrophilic colloid layers, including radiation-sensitive silver halide emulsion layers, forming layer units for separately recording blue, green, and red exposures, each of the layer units containing dye image-forming coupler chosen to produce image dye having an absorption half-peak bandwidth lying in a different spectral region in each layer unit, wherein the layer units are substantially free of colored masking coupler, the layer units each exhibit a dye image gamma of less than 1.5, the element exhibits an exposure latitude of at least 2.7 log E, where E is exposure measured in lux-seconds, and a light sensitivity of at least ISO 50, and wherein the gamma ratio for each of the blue, and red color recording units is between 0.8 and 1.2.
In another aspect, this invention is directed to a color negative photographic element suited both for preloading in a one-time-use camera and for producing a color image suited for conversion to an electronic form and subsequent reconversion into a viewable form, said element comprising a support and, coated on the support, a plurality of hydrophilic colloid layers, including radiation-sensitive silver halide emulsion layers, forming layer units for separately recording blue, green, and red exposures, each of the layer units containing dye image-forming coupler chosen to produce image dye having an absorption half-peak bandwidth lying in a different spectral region in each layer unit, WHEREIN the layer units are substantially free of colored masking coupler, the layer units each exhibit a dye image gamma of less than 1.5, the element exhibits an exposure latitude of at least 2.7 log E, where E is exposure measured in lux-seconds, and a light sensitivity of at least ISO 50, and the gamma ratio of each of the red and blue light recording layer units is between 0.80 and 1.20.
In a further embodiment, this invention is directed to a method of chemically developing an image exposed onto the described photographic element.
In yet another aspect, this invention is directed to a method of creating density representative electronic signals which may be employed to form a viewable image from a color negative photographic element suited both for preloading in a one-time-use camera and for producing a color image suited for conversion to an electronic form and subsequent reconversion into a viewable form comprising the steps of:
A) scanning an imagewise exposed and color developed color negative photographic element, said element comprising a support and, coated on the support, a plurality of hydrophilic colloid layers, including radiation-sensitive silver halide emulsion layers, forming layer units for separately recording blue, green, and red exposures, each of the layer units containing dye image-forming coupler chosen to produce image dye having an absorption half-peak bandwidth lying in a different spectral region in each layer unit, WHEREIN the layer units are substantially free of colored masking coupler, the layer units each exhibit a dye image gamma of less than 1.5, the element exhibits an exposure latitude of at least 2.7 log E, where E is exposure measured in lux-seconds, and a light sensitivity of at least ISO 50, and the gamma ratio of each of the red and blue light recording layer units is between 0.80 and 1.20, to form density representative electronic signals for said red, green, and blue color recording units,
B) electronically manipulating said density representative electronic signals formed in step A to correct either or both interimage interactions and gamma mismatches among said color records so as to produce an electronic record of said corrected color image, and
C) transmitting, storing, printing, or displaying said electronic record.
In yet another embodiment, this invention is directed to a method of electronically processing an image from a scene exposed onto a color negative photographic element suited for preloading in a one-time-use camera and for producing a color image suited for conversion to an electronic form and subsequent reconversion into a viewable form comprising the steps of sequentially:
a) converting scanner generated red, green, and blue image-bearing signals from an imagewise exposed, color developed and color scanned color negative photographic element to corresponding red, green, and blue scanner-density signals;
said element comprising a support and, coated on the support, a plurality of hydrophilic colloid layers, including radiation-sensitive silver halide emulsion layers, forming layer units for separately recording blue, green, and red exposures, each of the layer units containing dye image-forming coupler chosen to produce image dye having an absorption half-peak bandwidth lying in a different spectral region in each layer unit, WHEREIN the layer units are substantially free of colored masking coupler, the layer units each exhibit a dye image gamma of less than 1.5, the element exhibits an exposure latitude of at least 2.7 log E, where E is exposure measured in lux-seconds, and a light sensitivity of at least ISO 50, and the gamma ratio of the blue light recording layer units is between 0.80 and 1.20;
b) matrix transforming said red, green, and blue scanner-density signals to channel dependent red, green, and blue image-bearing signals,
c) modifying said channel dependent red, green, and blue image-bearing signals to correct for gamma mismatches or errors using a one-dimensional look-up table to form corrected channel dependent red, green, and blue image-bearing signals
d) transforming said corrected channel dependent red, green, and blue image-bearing signals to red, green, and blue output image-bearing signals using a one-dimensional look-up table; and
e) transmitting, storing, printing or displaying said red, green, and blue output image-bearing signals.
The invention provides a film suitable for use in a single-use camera that provides excellent images after scanning and electronic conversion.